Bicomponent fibers having contaminant-containing core domain and methods of making the same

ABSTRACT

Novel bicomponent fibers have a polyamide domain and a contaminant-containing polymer domain which is embedded entirely within, and thereby completely surrounded by, the polyamide domain. The preferred bicomponent fibers have a sheath-core structure wherein the polyamide domain constitutes the sheath and the contaminant-containing polymer constitutes the core. Surprisingly, even though the core is formed of a contaminant-containing polymer (which is difficultly spinnable), the bicomponent fibers are readily spinnable and exhibit properties which are comparable in many respects to fibers formed from 100% polyamide. Preferably, the fibers are concentric sheath-core bicomponent fibers having an uncontaminated nylon-6 sheath and a core formed from nylon-6 having a relatively high level of contamination in the form of the cyclic dimer of caprolactam and/or nylon-6 derived from colored regenerated post-consumer nylon carpet fibers.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 08/998,830,filed Dec. 29, 1997 now U.S. Pat. No. 5,885,705. This application isrelated to, and claims domestic priority benefits from, U.S. Provisionalpatent application Ser. No. 60/034,745 filed on Jan. 10, 1997, theentire content of which is expressly incorporated hereinto by reference.

FIELD OF INVENTION

The present invention relates generally to the field of syntheticfibers. More particularly, the present invention relates to syntheticbicomponent fibers having a sheath-core structure. In particularlypreferred forms, the present invention is embodied in multi-lobalbicomponent fibers having a polyamide sheath entirely surrounding a coreformed of a contaminant-containing polymeric material.

BACKGROUND AND SUMMARY OF THE INVENTION

Polyamide has been utilized extensively as a synthetic fiber. While itsstructural and mechanical properties make it attractive for use in suchcapacities as carpeting, it is nonetheless relatively expensive. Itwould therefore be desirable to replace a portion of polyamide fiberswith a core formed from a relatively lower cost material.

In this regard, some polymeric materials that are attractive candidatesas a partial replacement of the polyamide are "off-specification"--thatis, contain a contaminant. For example, "off-specification" nylon-6having relatively high levels of the cyclic dimer of caprolactam isparticularly troublesome when attempted to be melt-spun. Such"off-specification" nylon 6 can be obtained from a number of sourcesdue, for example, to its being manufactured with methods that producehigh levels of the cyclic dimer contaminant, or have avoided (orminimally exposed) to a dimer extraction step. However, replacing aportion of a 100% polyamide fiber with a core portion of a contaminantmaterial may affect the mechanical properties of the fiber to an extentthat it would no longer be useful in its intended end-use application(e.g., as a carpet fiber).

Furthermore, many regenerated polymeric materials are already colored(e.g., by use of a colorant or dye). Therefore, their use as a materialto make useful products (e.g., carpet fibers) is usually limited by thecolor of the regenerated polymeric materials that may be obtained.Typically, only clear regenerated polymeric materials are employed forsuch purposes since the manufacturer can then add pigments or dyes toprovide products of desired color.

Recently, U.S. Pat. No. 5,549,957 has proposed multi-lobal compositefibers having a nylon sheath and a core of a fiber-forming polymer whichcan be, for example, "off spec" or reclaimed polymers. (Column 4, lines6-8.) The core can be polypropylene, polyethylene terephthalate, highdensity polyethylene, polyester or polyvinyl chloride. (Column 4, lines17-20.) The core is covered with a sheath of virgin nylon whichconstitutes between 30% to 50% by weight of the core/sheath fiber.(Column 3, lines 65-67.)

The presently known prior art therefore evidences the fact thatcontaminant-containing polymeric materials--particularly, nylon-6 havinga relatively high level of the cyclic dimer of caprolactam--have notbeen employed as a structural component of finished bicomponentsynthetic fiber structures.

Broadly, the present invention relates to a bicomponent fiber structurehaving a polyamide domain and another distinct cross-sectional domainformed of polymeric material having a relatively high level ofcontaminant. The contaminant-containing polymeric domain is embeddedentirely within, and thus completely surrounded by, the polyamidedomain. Preferably, the fibers of this invention have a concentricsheath-core structure whereby the polyamide domain forms the sheath andthe contaminant polymer forms the core. Surprisingly, even though thecore is formed of a polymer having relatively high levels ofcontaminant, the bicomponent sheath-core fibers of this inventionexhibit properties which are comparable in many respects to fibersformed from 100% (virgin) polyamide.

In another aspect, the present invention relates to a bicomponent fiberstructure having a polyamide domain and another distinct cross-sectionaldomain formed of a regenerated colored polymeric material. Theregenerated polymeric domain is embedded entirely within, and thuscompletely surrounded by, the polyamide domain. Preferably, the fibersof this invention have a concentric sheath-core structure whereby thepolyamide domain forms the sheath and the regenerated polymer forms thecore. Surprisingly, even though the core is formed of a regeneratedcolored polymeric material, the bicomponent sheath-core fibers of thisinvention exhibit properties which are comparable in many respects tofibers formed from 100% (virgin) polyamide. For example, the virginpolymer sheath component of the bicomponent fibers of this invention canbe colored to an extent that the colored regenerated polymeric corematerial in the core is "hidden".

A further aspect of this invention is that the colored regeneratedpolymeric material be blended with a color-leveler--for example, a blackpigment, such a carbon black. In this regard, it is known that mostregenerated (recycled) polymeric materials will have some colorvariation, typically a shade of gray-green. According to the presentinvention, therefore, the regenerated colored polymeric material wouldfirst be measured against a known color standard. A specified amount ofa color leveler (e.g., carbon black) would then be added to theregenerated colored polymeric material to correct its color to the knownstandard. Thereafter, the color-corrected regenerated polymeric materialmay be incorporated into the core of a sheath-core fiber according tothis invention.

These, as well as other aspects and advantages of this invention, willbecome more apparent after careful consideration is given to thefollowing detailed description of the preferred exemplary embodimentsthereof.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

As used herein and in the accompanying claims, the term "fiber-forming"is meant to refer to at least partly oriented, partly crystalline,linear polymers which are capable of being formed into a fiber structurehaving a length at least 100 times its width and capable of being drawnwithout breakage at least about 10%. The term "non-fiber-forming" istherefore meant to refer to polymers which may be formed into a fiberstructure, but which are incapable of being drawn without breakage atleast about 10%.

The term "fiber" includes fibers of extreme or indefinite length(filaments) and fibers of short length (staple). The term "yarn" refersto a continuous strand or bundle of fibers.

The term "bicomponent fiber" is a fiber having at least two distinctcross-sectional domains respectively formed of different polymers. Theterm "bicomponent fiber" is thus intended to include concentric andeccentric sheath-core fiber structures and island-in-sea fiberstructures. Preferred according to the present invention are concentricbicomponent sheath-core fiber structures having a polyamide sheath and acontaminant-containing polymer core, and thus the disclosure whichfollows will be directed to such a preferred embodiment. However, thepresent invention is equally applicable to other bicomponent fiberstructures having a polyamide domain and a non-fiber-formingcontaminant-containing polymer domain embedded entirely within, and thuscompletely surrounded by, the polyamide domain.

The term "linear polymer" is meant to encompass polymers having astraight chain structure wherein less than about 10% of the structuralunits have side chains and/or branches.

The terms "contaminated" and "uncontaminated" refer to a difference inthe presence of an undesirable contaminant component wherein the"uncontaminated" material has less than 80% of the component presentthan the "contaminated" material. Furthermore, the "uncontaminated"material when spun as a single component fiber forming resin exhibits50% less spinning interruptions than the "contaminated material" whenspun into a similar fiber. In this regard, a spinning interruption is anevent in the extrusion of fiber of filaments wherein the continuousproduction of fiber or filaments is interrupted. One major cause isthreadline instability due to deposits on the spinneret face. Suchevents reduce the capacity of spinning equipment, produce waste, andoften result in less than full yarn packages.

The term "regenerated polymer" is meant to refer to recycledpost-consumer polymeric waste materials which are, in and of themselves,non-fiber-forming. Thus, a "regenerated polymer" in accordance with thepresent invention is encompassed within the definition of a contaminantcomponent.

The preferred polyamides useful to form the sheath of the bicomponentfibers of this invention are those which are generically known by theterm "nylon" and are long chain synthetic polymers containing amide(--CO--NH--) linkages along the main polymer chain. Suitable meltspinnable, fiber-forming polyamides for the sheath of the sheath-corebicomponent fibers according to this invention include those which areobtained by the polymerization of a lactam or an amino acid, or thosepolymers formed by the condensation of a diamine and a dicarboxylicacid. Typical polyamides useful in the present invention include nylon6, nylon 6/6, nylon 6/9, nylon 6/10, nylon 6T, nylon 6/12, nylon 11,nylon 12, nylon 4,6 and copolymers thereof or mixtures thereof.Polyamides can also be copolymers of nylon 6 or nylon 6/6 and a nylonsalt obtained by reacting a dicarboxylic acid component such asterephthalic acid, isophthalic acid, adipic acid or sebacic acid with adiamine such as hexamethylene diamine, methaxylene diamine, or1,4-bisaminomethylcyclohexane. Preferred are poly-ε-caprolactam (nylon6) and polyhexamethylene adipamide (nylon 6/6). Most preferred is nylon6.

Importantly, the core of the sheath-core fibers according to thisinvention is formed of a polymeric material which contains relativelyhigh levels of contaminants. Most preferably, the contaminant-containingpolymer forming the core of the sheath-core fibers is compatible withthe polyamide sheath. For example, if uncontaminated nylon-6 is employedas the sheath polymer then contaminate-containing nylon-6 is employed asthe core polymer. The amount of contaminant in the core polymer shouldbe at least about three times greater than any residual contaminantsthat may be present in the sheath polymer.

The core will preferably represent about 50% or greater by weight of thetotal bicomponent fiber weight according to this invention, with thesheath representing about 50 wt. % or less. Surprisingly, when the coreis formed of contaminated nylon-6 and represents about 80 wt. % of thebicomponent fiber, physical attributes comparable to fibers formed of100% nylon-6 are achieved.

The sheathcore fibers are spun using conventional fiber-formingequipment. Thus, for example, separate melt flows of the sheath and corepolymers may be fed to a conventional sheath-core spinneret pack such asthose described in U.S. Pat. Nos. 5,162,074, 5,125,818, 5,344,297 and5,445,884 (the entire content of each patent being incorporatedexpressly hereinto by reference) where the melt flows are combined toform extruded multi-lobal (e.g., tri-, tetra-, penta- or hexalobal)fibers having sheath and core structures. Preferably, the fibers have atrilobal structure with a modification ratio of at least about 2.0, morepreferably between 2.2 and 4.0. In this regard, the term "modificationratio" means the ratio R₁ /R₂, where R₂ is the radius of the largestcircle that is wholly within a transverse cross-section of the fiber,and R₁ is the radius of the circle that circumscribes the transversecross-section.

The extruded fibers are quenched, for example with air, in order tosolidify the fibers. The fibers may then be treated with a finishcomprising a lubricating oil or mixture of oils and antistatic agents.The thus formed fibers are then combined to form a yarn bundle which isthen wound on a suitable package.

In a subsequent step, the yarn is drawn and texturized to form a bulkedcontinuous fiber (BCF) yarn suitable for tufting into carpets. A morepreferred technique involves combining the extruded or as-spun fibersinto a yarn, then drawing, texturizing and winding into a package all ina single step. This one-step method of making BCF is generally known inthe art as spin-draw-texturing (SDT).

Nylon fibers for the purpose of carpet manufacturing have lineardensities in the range of about 3 to about 75 denier/filament (dpf)(denier=weight in grams of a single fiber with a length of 9000 meters).A more preferred range for carpet fibers is from about 15 to 28 dpf.

The BCF yarns can go through various processing steps well known tothose skilled in the art. For example, to produce carpets for floorcovering applications, the BCF yarns are generally tufted into a pliableprimary backing. Primary backing materials are generally selected fromwoven jute, woven polypropylene, cellulosic nonwovens, and nonwovens ofnylon, polyester and polypropylene. The primary backing is then coatedwith a suitable latex material such as a conventional styrene-butadiene(SB) latex, vinylidene chloride polymer, or vinyl chloride-vinylidenechloride copolymers. It is common practice to use fillers such ascalcium carbonate to reduce latex costs. The final step is to apply asecondary backing, generally a woven jute or woven synthetic such aspolypropylene. Preferably, carpets for floor covering applications willinclude a woven polypropylene primary backing, a conventional SB latexformulation, and either a woven jute or woven polypropylene secondarycarpet backing. The SB latex can include calcium carbonate filler and/orone or more the hydrate materials listed above.

While the discussion above has emphasized the fibers of this inventionbeing formed into bulked continuous fibers for purposes of making carpetfibers, the fibers of this invention can be processed to form fibers fora variety of textile applications. In this regard, the fibers can becrimped or otherwise texturized and then chopped to form random lengthsof staple fibers having individual fiber lengths varying from about 11/2to about 8 inches.

The fibers of this invention can be dyed or colored utilizingconventional fiber-coloring techniques. For example, the fibers of thisinvention may be subjected to an acid dye bath to achieve desired fibercoloration. Alternatively, the nylon sheath may be colored in the meltprior to fiber-formation (i.e., solution dyed) using conventionalpigments for such purpose.

A further understanding of this invention will be obtained from thefollowing non-limiting Examples which illustrate specific embodimentsthereof.

EXAMPLES

Physical properties for the samples in the Examples below were obtainedusing the following test procedures:

Vetterman Drum Wear: The Vetterman Drum test simulated wear according toASTM D5417. The degree of wear exhibit by the samples is determined by avisual rating relative to photographic standards of wear from The Carpetand Rug Institute (CRI Reference Scale available from CRI, P.O. Box2048, Dalton, Georgia, USA). Each of the common types of carpetconstruction has a corresponding set of photographic examples of unwornand worn samples. The wear levels are from 5 to 1, where 5 represents novisible wear and 1 represents considerable wear.

Static Compression: The static compression was determined by testingfour samples from the material. Initial pile height of each carpetsample was determined under a load of 0.5 psi using the compressometerand methods as described above in determining Pile Height Retention. Thecarpet was compressed for 24 hours under 50 psi. The compression forcewas then removed and the carpet vacuumed and allowed to recover with noloading for another 24 hours, following which the final reading wasdone. The result was the average for the four samples reported as apercent of the original pile height. Testing and measurements wereconducted at 70° F. and 65% relative humidity.

Mass on A1 Foil (Mass AF): The mass deposited on aluminum foil wasdetermined by dissolving deposits using methanol, after which there wasno residue remaining on the foil. The weight of the foil before andafter methanol extraction was determined with the mass of the deposit inmilligrams being determined by the difference between such weightdeterminations.

Amount of Cyclic Oligomers: The amount of cyclic oligomers weredetermined by HPLC techniques. Retention times were determined fromknown standards. The percent (%) oligomers present was assumed to beproportional to the area under the peak for each signal. Estimates ofmass were determined by multiplying the percent of the component by themass removed from the aluminum foil.

Example 1 comparative

Nylon-6 polymerized under a high dimer process was spun at 275° C.through a 58 hole trilobal spinneret. The spin beam was bicomponent andboth extruders extruded the high dimer nylon-6. The polymer ratios fromthe two extruders (as determined by the polymer gear pump speed)produced a 20 wt. % sheath. The polymer throughput per hole was 3.44grams per minute (g/min). At the spinneret, aluminum foil surrounded thefiber bundle. The amount and relative composition of deposits on thealuminum foil are reported in Table 1 below. This example gave someproblems in spinning, requiring several stoppages.

Example 2 comparative

Commercial spinning grade nylon 6 (BS 700-F from BASF Corporation of Mt.Olive, N.J.) was spun at 275° C. through a 58 hole trilobal spinneret.The spin beam was bicomponent and both extruders extruded the commercialspinning grade nylon-6. The polymer ratios from the two extruders (asdetermined by the polymer gear pump speeds) produced a 20 wt. % sheath.The polymer throughput per hole was 3.44 grams per minute (g/min). Thespinning speed (speed of the first driven roll in the take-up process)was 500 meters per minute (M/min). At the spinneret, aluminum foilsurrounded the fiber bundle. The amount and relative composition ofdeposits on the aluminum foil are reported in Table 1 below. Thisexample gave no problems in two hours of spinning.

Example 3 invention

A sheath-core bicomponent trilobal fiber was created using the apparatusof examples 1 and 2. Nylon-6 polymerized from a high dimer processformed the 80 wt. % by weight core and commercial spinning grade nylon-6(BS-700F from BASF Corporation of Mt. Olive, N.J.) formed the 20 wt. %sheath. Both polymers were spun at 275° C. through a 58 hole trilobalspinneret. The spin beam was bicomponent. The polymer ratios from thetwo extruders (as determined by the polymer gear pump speed) produced a20 wt. % sheath. The polymer throughput per hole was 3.44 grams perminute. The spinning speed (speed of the first driven roll in the takeupprocess) was 500 meters per minute. At the spinneret, aluminum foilsurrounded the fiber bundle. The amount and relative composition ofdeposits on the aluminum foil are reported in Table

1. This example gave no problems in two hours of spinning.

                  TABLE 1                                                         ______________________________________                                        Residues from Examples 1-3                                                         AF                          Capro CD                                     Ex.  Mass                        Mass  Mass CT Mass                           No.  (gm)   % Capro  % CD  % CT  (gm)  (gm) (gm)                              ______________________________________                                        1    42.2   3        92     5    1.4   38.8 2.1                               2    11.2   5        80    14     .6    9.0 1.6                               3    20.0   NS       98     2    NS    19.5 0.5                               ______________________________________                                         Notes:                                                                        AF Mass = Mass on aluminum foil                                               Capro = Caprolactam                                                           CD = cycli dimer                                                              CT = cyclic trimer                                                            NS = Not Sufficient signal to determine content                          

Example 4 invention

A sheath-core bicomponent trilobal fiber was created using the apparatusof examples 1 and 2. Nylon-6 polymerized from a high dimer processformed the 80 wt. % by weight core and commercial spinning grade nylon-6(BAS-700F from BASF Corporation of Mt. Olive, N.J.) through a 58 holetrilobal spinneret. The spin beam was bicomponent. The polymer ratiosfrom the two extruders (as determined by the polymer gear pump speed)produced a 20 wt. % sheath. The polymer throughput per hole was 3.44grams per minute. The spinning speed (speed of the first driven roll inthe take-up process) was 500 meters per minute. At the spinneret,aluminum foil surrounded the fiber bundle. The amount and relativecomposition of deposits on the aluminum foil are reported in Table 2.This example gave no problems in 31/2 hours of spinning. The yarn wasdrawn to a draw ratio of 3:1 and wound on a winder at a speed ofapproximately 1600 meters per minute. Spinning and drawing were done inone step. This yarn was subsequently steam textured.

Two ends of this yarn were cabled and twisted to a nominal twist of 4.5twists per inch. The cabled yarn was then autoclaved heatset using aheating cycle of 265° F.-240° F.-265° F.-240° F.-265° F. The yarn wasthen tufted into a 1/8 gage cut pile carpet with 40 ozs. of face fiberper square yard of carpet with a 1/2-inch pile height. Carpets were dyedto a light brown shade and coated with latex. Vetterman drum and staticcompression test results are reported in Table 2.

Example 5 invention

Example 4 was repeated, except that the nylon-6 with high dimer contentis in a 50 wt. % core and the sheath of commercial spinning gradenylon-6 formed a 50 wt. % sheath. Spinning performance was very good.Carpet testing results are reported in Table 2.

Example 6 comparative

Examples 4 and 5 were repeated, except that the fibers consisted of 100%high cyclic dimer content nylon-6. Spinning performance was much poorerthan that seen in Examples 4 and 5. Processing the fiber into carpetswas fine and the wear and compression properties of the carpets isreported in Table 2.

Example 7 Comparative

Examples 4 and 5 were repeated, except that the fibers consisted of 100%commercial spinning grade nylon-6 BS-700F from BASF Corporation of Mt.Olive, N.J.). Spinning performance was equivalent to that seen inExamples 4 and 5. Processing the fiber into carpets was fine and thewear and compression properties of the carpets is reported in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Carpet Performance from Examples 4-7                                          Vetterman Drum Simulated Wear                                                 5,000 Cycles     22,000 Cycles                                                          Pile Height   Pile Height                                                                          Static                                         Visual Grade                                                                            Retention (%)                                                                        Visual Grade                                                                         Retention (%)                                                                        Compression (%)                                __________________________________________________________________________    Ex. 4                                                                            3-4    88     1-2    81     95                                             Ex. 5                                                                            3      87     1-2    79     86                                             Ex. 6                                                                            3-4    91     2-3    79     87                                             Ex. 7                                                                            3-4    89     1-2    87     95                                             __________________________________________________________________________

The data above demonstrate that bicomponent fibers according to thisinvention will exhibit properties that are comparable to fibers formedfrom 100% uncontaminated nylon-6.

Example 8 invention

Nylon 6 polymer (Ultramid® BS-700F nylon commercially available fromBASF Corporation) and a regenerated polymeric material obtained fromrecycled nylon carpets having 90% nylon 6 and 10% dirt and backingcontaminants are used in this Example 8. The materials are extrudedusing equipment as described in U.S. Pat. No. 5,244,614. The relativeamounts of each component are 75 wt. % nylon 6 in the sheath and 25 wt.% recycled nylon 6 in the core. Final extruder zone temperatures foreach polymer are 275° C. for the nylon 6 and 275° C. for the recyclednylon 6. The spin pack temperature is 270° C. The polymers are deliveredto a spin pack designed using thin plates such as described in U.S. Pat.No. 5,458,972 (the entire content of which is incorporated hereinto byreference), particularly FIG. 4 thereof so as to form a trilobalbicomponent fiber having a concentric circular cross-section core. Thefiber is cooled, drawn and textured in a continuous spin-draw apparatus(Rieter J0/10). The draw ratio is 2.8 and the winding speed is 2200meters per minute.

Example 9 invention

Nylon 6 polymer (Ultramid® BS-700F nylon commercially available fromBASF Corporation) and a regenerated polymeric material obtained fromrecycled nylon carpets having 90% nylon 6 and 10% dirt and backingcontaminants are used in this Example 9. The materials are extrudedusing equipment as described in U.S. Pat. No. 5,244,614. The relativeamounts of each component are 70 wt. % nylon 6 in the sheath and 30 wt.% recycled nylon 6 in the core. Final extruder zone temperatures foreach polymer are 275° C. for the nylon 6 and 275° C. for the recyclednylon 6. The spin pack temperature is 270° C. The polymers are deliveredto a spin pack designed using thin plates such as described in U.S. Pat.No. 5,458,972 so as to form a trilobal bicomponent fiber having aconcentric circular cross-section primary core and a radially elongate,elliptically cross-section secondary core in each of the trilobal fiberlegs. The fiber is cooled, drawn and textured in a continuous spin-drawapparatus (Rieter J0/10). The draw ratio is 2.8 and the winding speed is2200 meters per minute.

Example 10 invention

It is known that recycled polymeric material will have some colorvariation (typically a shade of gray-green) due to the different colorsand polymers between batches of recycled material. The recycled polymeris thus measured for color difference against a known color standard.Thereafter, a specified amount of carbon black is added to the recycledpolymer to correct the color to the known standard color. The"color-leveled" recycled polymer could then be spun as a core in thefibers according to Examples 8 and 9.

Example 11 invention

The core material of post consumer recovered nylon 6 was processed usingthe techniques described in U.S. Pat. No. 5,535,945 (incorporatedhereinto by reference) The starting materials were colored, backedcarpets of nylon 6 face yarn obtained from carpets that had been wornand were being replaced. The carpet was ground and much of the backingmaterial is separated via a centrifuge and a polymer filtration step.The resultant polymer material was approximately 95% nylon 6. Theremaining 5% was composed of latex house dirt and possibly othercontaminant components, as well as polypropylene and residual colorants.

The recovered nylon 6 was melt spun in the core of a sheath-coretrilobal fiber. The sheath material was BS-700F (BASF Corporation, MountOlive, N.J.) with no additives. Polymer temperatures were each 270° C.The sheath was 75% of the fiber by weight while the core was 25% of thefiber weight. The spinning apparatus was a bicomponent spin head thatutilized thin plates such as those described in U.S. Pat. No. 5,344,297.A conventional one-step bulked continuous fiber (BCF) carpetdrawing-texturing, and winding machine was used. Winding speed wasapproximately 2050 m/min. Physical properties of these yarns measuredaccording to ASTM D 2256-97 appear in Table 3 below. The yarn had amedium green color.

Example 12 invention

Example 10 was repeated, except that approximately 1.60% of a greenpigment mixture was added to the BS-700F nylon-6 in the sheath resultingin 1.2 percent pigment added to the total fiber. No colorant was addedto the core material. These fibers were a darker green as compared tothe fibers obtained in Example 10. Physical properties of these yarnsare summarized in Table 3 below.

Example 13 comparative

Example 12 was repeated, except that the core of the fibers was brightuncolored BS-700F nylon-6. These fibers are a lighter shade of green ascompared to the fibers obtained in Examples 11 and 12. Physicalproperties of the yarns are summarized in Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Physical Properties of Fibers                                                 Linear   Modifica-         Breaking Modulus @                                 Density  tion     Tenactiy Elongation                                                                             5% extension                              (denier) Ratio    (g/denier)                                                                             (% extension)                                                                          (g/denier)                                ______________________________________                                        Ex.  1253    2.76     2.61   17.1     7.50                                    11                                                                            Ex.  1241    2.74     2.72   35.6     6.80                                    12                                                                            Ex.  1211    2.76     3.01   38.6     8.16                                    13                                                                            ______________________________________                                    

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A bicomponent fiber comprising a colored,recreated polymeric core surrounded by a virgin polyamide, coloredsheath, said sheath being colored to an extent that the color of saidregenerated polymeric core is not visible.
 2. A fiber as in claim 1,wherein each of the core and sheath domains is nylon.
 3. A fiber as inclaim 2, wherein the nylon is nylon-6.
 4. The bicomponent fiber of claim1, comprising a core formed of a regenerated polymer having caprolactamcyclic dimer and a sheath entirely surrounding said core, wherein saidcore includes a color leveler.
 5. The fiber of claim 4, wherein thecolor leveler is carbon black.
 6. A fiber as in claim 4, in the form ofa trilobal, concentric sheath-core bicomponent fiber.
 7. A fiber as inclaim 6, wherein the nylon sheath is nylon 6 or nylon 6/6.
 8. A fiber asin claim 7, wherein the core comprises 50% by weight or greater of thefiber.
 9. A fiber as in claim 8, wherein the sheath comprises greaterthan about 75% by weight of the fiber, and the core comprises less thanabout 25% by weight of the fiber.
 10. A fiber as in claim 1 or 4, whichis drawn greater than 10%.
 11. A fiber as in claim 1 or 4, which is abulked continuous carpet fiber.
 12. A fiber as in claim 1 or 4, which isa staple fiber.
 13. A yarn comprised of a plurality of carpet fibers asin any one of claims 1-4.
 14. A fabric comprised of a plurality offibers as in any one of claims 1-4.